A phosphorescent sensor for detection of Micrococcal nuclease base on phosphorescent resonance energy transfer between quantum dots and DNA-ROX

To solve interference from background fluorescence and scattering light of real biological samples, we developed a room-temperature phosphorescence (RTP) sensor to detect Micrococcal nuclease (MNase). The sensor was based on the phosphorescent resonance energy transfer (PRET) between 3-mercaptopropionic acid (MPA)-capped Mn-doped ZnS quantum dots (QDs) and single-marked oligonucleotide (DNA-ROX). Specifically, the poly-(diallyldimethylammonium chloride) (PDAD)-modified QDs (PDAD-QDs) were prepared as the energy donor, and the DNA-ROX was chosen as the energy receptor. The DNA-ROX could be adsorbed to the surface of the PDAD-QDs through electrostatic interaction, which induced PRET and quenched the RTP of PDAD-QDs. The MNase could efficiently degrade the DNA-ROX into small DNA segments, which were less prone to electrostatic interaction with PDAD-QDs, and thus the PRET efficiency decreased. The RTP intensity of PDAD-QDs was gradually enhanced with the increment of MNase concentration. Under the optimal conditions, the change of RTP intensity was proportional to the logarithm of MNase concentration in the range from 2 × 10−3 to 8.0 × 10−2 U mL−1, with a high correlation coefficient of 0.993 and a detection limit of 6 × 10−4 U mL−1. This proposed RTP sensor can avoid interferences from the background fluorescence or scattering light of the matrix that are encountered in spectrofluorometry. Thus, this biosensor can be applied to detect MNase in culture media.